Burst Alert! March 19th was an exciting day for NASA. We know “why” it was special, but we don’t know “why why” it was special. They finally explain the why why today, and you can read all about it in Nature tomorrow.
There was something amazing about GRB 080319B and the other cosmic bursts that NASA’s Swift satellite detected that day. (See NASA's animation of what they think happened).
"Even by the standards of gamma-ray bursts, this burst was a whopper," says Swift lead scientist Neil Gehrels of NASA. "It blows away every gamma ray burst we’ve seen so far."
Here’s the why (we'll get to the why why in a second):
Artist's interpretation of GRB 080319B. Credit: NASA/Swift/Mary Pat Hrybyk-Keith and John Jones.
The optical afterglow was 2.5 million times more luminous than the most luminous supernova ever recorded, making it the most intrinsically bright object ever observed by humans in the universe. It was so bright that immediately after the blast, Swift's UltraViolet and Optical Telescope and X-Ray Telescope indicated they were effectively blinded, originally leading researchers to think something had gone wrong.
"For a few precious seconds, the luminosity was a million times that of the whole galaxy," explains Dieter Hartmann, a Professor at Clemson University.
And on top of that, the burst shattered the record for the farthest object that’s ever been visible to the naked eye. The previous record was a spiral galaxy called M33, which is thousands of times closer than the March 19 explosion.
The explosion, which took place halfway across the universe, was so far away that it took its light 7.5 billion years to reach the Earth. In fact, the explosion took place so long ago that neither the Earth nor the Sun had come into existence.
If something like this happened closer to home, we would be in deep trouble. David Burrows, NASA's Swift X-ray Telescope leader at Penn State, says, "if it happened in our own galaxy, it could cause chemical changes that cause something like a nuclear winter. We don't believe there are any stars in our galaxy that are likely to become gamma ray bursts, but it is possible that an event like this may have happened in our galaxy in the past and lead to mass extinctions."
If you're having trouble grasping the magnitude of such an occurrence, don't feel bad. Hartmann explained that you can't really come up with an analogy to put the amount of energy that's being released into terms that 'normal' people would understand. "Those numbers are staggering," he says.
And 'normal' isn't used pejoratively. Even astrophysicists are blown away. Grigory Beskin, the Relativistic Astrophysics Group Head at the Special Astrophysical Observatory, said, "this is a true miracle to see such an optical flare."
Astronomers began their scientific analysis beginning 30 minutes before the explosion, and after following its afterglow for months, they’re ready to talk. Until recently they didn’t know the why why: why it was so powerful, and why the afterglow was so much brighter than other afterglows.
It turns out that a jet of material shot out from this dying supernova almost directly toward the Earth at 99.99995 percent the speed of light.
Judith Racusin, a graduate student at Penn State and one of the presenters at the NASA press conference today, explained that through unlikely circumstances, we got a chance to see something amazing with this jet, and it's changing the way astrophysicists are thinking.
"What's interesting about this burst, is that both the optical afterglow and the X-ray afterglow are inconsistent with our current theoretical understanding of how these objects work. It's forced us to really test our understanding of these objects, and as a result we've had to come up with an alternative explanation."
So NASA scientists have come up with a two-component jet model, in which there is both a wider outer jet (characteristic of what we usually see with these objects), and a narrow inner jet.
Hartmann says the narrow jet was just 0.4 of a degree across, while the less-energetic, wider jet was about 20 times wider.
"The narrow jet just happened to be pointed almost precisely at the Earth this time, which makes us think that most of the time, the narrow jet just isn't pointed directly at us. It's allowed us to see these objects in a new way," says Racusin.
The NASA scientists realize that sometimes better data spell trouble for simple models.
"But on the bright side," says Hartmann, "it's leading to new theoretical models!"
Related: Even NASA astrophysicists have self-doubt! Interview with NASA Dr. Kathy Flanagan.